Several patents have been written relating to the synthesis of water soluble, dispersible, or emulsifiable polyester resins. For example, Altenberg, in U.S. Pat. No. 4,604,410, has proposed making etherified aromatic polyols by digesting scrap polyalkylene terephthalate with a low molecular weight polyhydroxy compound, containing 3-8 hydroxyl groups. A resulting intermediate is alkoxylated with 1-4 moles of ethylene oxide and/or propylene oxide. The final product is useful in making polyurethane and polyisocyanurate foams.
Sperenza et al. U.S. Pat. No. 4,485,196 have recited reacting recycled polyethylene terephthalate scrap with an alkylene oxide, such as propylene oxide. The product can be used in making rigid foams.
Other methods of reacting scrap polyalkylene terephthalate with glycols or polyols are proposed by Svoboda et al. in U.S. Pat. No. 4,048,104; and Altenberg et al. U.S. Pat. No. 4,701,477. In applicant's previous invention (U.S. Pat. No. 4,977,191 to Salsman) there is disclosed a water-soluble or water-dispersible polyester resin suitable for textile sizing applications. The polyester resin comprises a reaction product of 20-50% by weight of waste terephthalate polymer, 10-40% by weight of at least one glycol and 5-25% by weight of at least one oxyalkylated polyol. Preferred compositions also comprise 20-50% by weight of isophthalic acid. A further water-soluble or water-dispersible resin comprises a reaction product of 20-50% by weight of waste terephthalate polymer, 10-50% by weight of at least one glycol and 20-50% by weight of isophthalic acid.
U.S. Pat. No. 5,252,615 to Rao et al teaches coating compositions derived from alcoholysis of polyethylene terephthalate (PET). Most preferably, the PET is recycled or reclaimed from plastic articles.
Dale et al., in U.S. Pat. No. 4,104,222, have proposed making a dispersion of linear polyester resins by mixing linear polyester resin with a higher alcohol/ethylene oxide addition-type surface-active agent, melting the mixture and dispersing the resulting melt in an aqueous alkali solution. The products are used as coating and impregnating agents.
References proposing the use of copolymers containing terephthalic units and units derived from alkylene and polyoxyalkylene glycols for fiber or fabric treatment include Hayes (U.S. Pat. No. 3,939,230), Nicol et al. (U.S. Pat. No. 3,962,152), Wada et al. (U.S. Pat. No. 4,027,346), Nicol (U.S. Pat. No. 4,125,370) and Bauer (U.S. Pat. No. 4,370,143).
Marshall et al., in U.S. Pat. No. 3,814,627, have proposed applying an ester, based on polyethylene glycol, to polyester yarn.
In our other U.S. Pat. No. 5,281,630 (Salsman), we disclose sulfonated water-soluble or water-dispersible polyester resin compositions made by treating a polyester glycolysis product with an alpha, beta-ethylenically unsaturated dicarboxylic acid and then with a sulfite.
The following U.S. patents describe polyester resins containing fatty acid moieties: U.S. Pat. Nos. 4,080,316; 4,179,420; 4,181,638; 4,413,116; 4,497,933; 4,517,334; 4,540,751; 4,555,564; 4,686,275; 5,075,417 and 5,530,059. None of the above patents disclose the resins of the present invention which have excellent hydrophobic and high contact angles when a drop of water is applied to surfaces coated with such resins.
The resins described in the above prior art have found applications in textiles, coatings, and adhesive. All of these resins however have a fairly polar nature which limits their use to adhesion promoters or coating applications where water resistance is not a major factor or where the water resistance is being supplied by other additives. No mention of water repellent properties has been associated with these polyester resins.
In some instances larger amounts of oils are fatty acids are used to supply cross-linking and thermosetting properties to the polyester resins. This chemistry has been labeled "alkyd" chemistry. During the drying phase cross-linking occurs between chains, and the applied coating becomes insoluble.
To this date the inventor has no knowledge of prior polyester art where the water dispersible or emulsifiable polyester resins of said art has incorporated enough non-polar groups to supply hydrophobic character or properties to the substrate on which these dispersions are applied and/or at the same time retain water redispersibility.
The main problem with most non-polar materials that have reactive condensation sites is that these materials have only one reactive site. (For example stearic acid, oleic acid, palmitic acid, behenic acid, etc. These are most likely isolated from naturally occurring triglycerides such as vegetable and animal fats and oils.) This means that in the polyester condensation reaction they become chain terminators and the amounts that can be used are severely limited because the greater the amount the less the molecular weight of the resin. In alkyd chemistry advantage is taken from the unsaturation in oils and cross linking reactions can be used. However reaction through unsaturation does not exposed sufficient areas of the oil modified chain to provide hydrophobic and water repellent properties to the coatings produced from this chemistry.
The resins described in this invention have overcome the problem of chain termination by using a highly modified polyester backbone. In this way polyester resins can be made containing 30 percent or more of monofunctional monomers, such as stearic acid, to provide a much improved non-polar nature. Then, using reactions cited in our previous patents, these resins can be made into water dispersions or emulsions. Because of the large amount of hydrophobic or non-polar functionality these resins cannot be considered water soluble as some previous sulfonated resins have been. When these dispersions or emulsions are applied to most substrates and dried, orientation of the hydrophobic areas of the chain occurs and the surface of the substrate becomes water repellent, with the degree of water repellency corresponding to the thickness and concentration of the initial coating. This water repellency is obvious from the high contact angle of a drop of distilled water placed on the substrate. This high contact angle is not evident in previous water dispersible resins.
The prior art is silent regarding the new water dispersible and polyester resins of the present invention which are derived from polyethylene terephthalate and which exhibits high water repellency as evidenced by high contact angles.